Scaffold systems have been proposed utilizing vertical posts, with the vertical posts being arranged at a spacing corresponding to a grid of the scaffold system. Horizontally and/or diagonally extended elongated scaffold elements are generally attached to the annular connecting members with connecting heads, and vertical outer boundary surfaces of the connecting heads are fashioned so as to converge in a wedge shape toward the post and disc center. The connecting heads are generally fashioned of cast steel, malleable cast iron or forged steel, and the connecting heads mounted to the elongated scaffold elements are centered and welded in position.
Connecting devices of the aforementioned type are disclosed in, for example, German Pat. No. 2,449,124 and, from practical uses, by the Company Layher...Eibensbach. Normally the connecting heads are manufactured from malleable cast iron and exhibit, for centering within the pipe to which the connecting head is to be connected, at least three studs or centering lobes adapted to an inner diameter of the pipe of the scaffold system. A positioning surface at an end face, slightly projecting beyond an inner diameter and located normal on the pipe axis, is constructed so as to be continuous only in a zone of the inner diameter of the pipe. External portions of the positioning surface are interrupted in regions of the lateral, vertically extending surfaces which are slightly inclined rearwardly in a direction toward the pipe of the scaffold system.
A disadvantage of the above proposed connecting heads resides in the fact that the mounting is not provided with a seam bottom which extends continuously and uniformly all around but rather an L-shaped seam bottom results in part and an I-shaped seam must then be laid in the lateral zones. By virtue of this fact, and due to the properties on the material, irregularities arise during the circumferential welding by automatic welding machines, which irregularities adversely effect the connecting heads and/or overall scaffold system.
In, for example, DE No. 3,236,4678 A1, a building scaffold system is provided which includes cup-like connecting elements disposed on the scaffold posts and hook-equipped connecting heads are suspended in the cup-like connecting elements. The connecting heads are attached to the elongated scaffold elements by welding and, for this purpose, an extension is provided, with the extension being adapted to a free end of the horizontal span and suitably fastened by a weld seam. To enable an insertion, centering and attachment, a continuous conical surface is provided without special auxiliary alignment means, leading to a weld bond having a substantially V-shaped seam or a substantially L-shaped seam. The exact alignment with respect to the pipe during welding requires a corresponding aligning of the auxiliary means since there is no abutment face or annular contact surface.
DE No. 3,121,141 A1 also proposes a cup-shaped connecting head which, for engagement into an end of an elongated scaffolding element, includes a centering insert with rounded end construction, with the insert being placed into the pipe end. During this insertion step, the inner rim of the pipe end is seated with very little defined accuracy on rounded transition areas between the connecting head and the stud and a chamfer at the pipe permits a provision of a V-seam.
DE No. 2,704,398 A1 also proposes a connection arrangement for a scaffold system wherein a keyhole-like insert element with a scaffold pipe is constructed so that a shaped wedge member with a straight surface is placed in front of a straight cut-off face of the pipe and is welded in partial regions by V-shaped weld seams.
Additionally, DE No. 3,005,182 A1 proposes a connecting head with the above described features and including a conventional extension for attachment to a pipe of the scaffold system.